detonation main cause of broken plugs just below engine coming apart

Just swapped out the EGR valve out of another intake I had sitting. Same result, but a lot harder to blow on to get the smoke coming out of it. I will put it all back together and start it and let you know what the cleaner does. Take it a break, its getting hot outside. LOL


I don't want to hear that, this poor cherokee has to last me a couple more years.

Don't lose hope yet. That eGR valve sould have been the source of a rather large internal vacuum leak.,

Not losing hope yet. With everyones help on here, Im sure we can figure this out. Little off topic put I still need to get you those pics of the ground refreshes. Make the pics smaller. I also did the Coil refresh and took pics of that to. I need to get those to ya.

I'm ready when you are.

Try this: Take your old EGR valve and try blowing from the pintle side into the valve. See if any air passes through. FWIW, your lips will be black, but it's a good thing to know.

Okay, don't know what the pintle side is?? but I just blew through all the holes. Im guessing your talking about the holes that meet up with the intake. The round hole, that has a vacuum pipe coming off it, I can't get any air to pass. While I am holding on to the vacuum pipe. The hole that looks like a mouth, I can pass air through it.

You shouldn't be able to blow air from the intake side if the valve is good. Make sense?

So no matter which hole, if I can pass air through either side, its bad. Right?? I sprayed throttle cleaner on the EGR I just put in and no change to the idle of the engine. I called the local parts store and they want 70 bucks for a new valve. I will have to wait on a new one of those.

You don't want exhaust gasses passing between the intake and exhaust sides of the valve without vacuum applied to the small port. Therefore, if you can blow from the "black" side of the valve with the pintle sticking out, there's a good chance the valve is bad.

So pretty sure the old one was bad. I will try this one and see how it does. I will keep checking the plug and see if it breaks and go from there. Wife is telling me Jeep play time is over and I need to come in. LOL Thanks for your help and I will keep you posted.

Smoke test showed no leaks - even underneath?

Compression readings look good!

Isn't the EGR located at the back of the engine? If so, it would affect #6 more than the rest.

Did you have any trouble putting on the intake/exhaust gasket when you put it together? No paper or packing material left inside? Sounds like a dumb question - but I've seen it twice.

At this point I'd want to take off the valve cover - to make sure the #1 exhaust valve is opening as far as the others (and the intake, but doubtful that's the problem. You can use a dial indicator - or just hold your finger on the rocker to feel and compare with other exhaust valves while running. They should all feel the same.
Wondering if the exhaust is backing up - like constipation - valve not opening far enough - rocker/lifter/cam etc.

The exhaust manifold - you welded it?
If it was restricted any where except the #1 runner, more plugs would be overheating - they aren't - by the pictures.

SOMETHING COMMON TO #1 CYLINDER ONLY - That eliminates most everything.

something's not letting the the exhaust gasses out - the incoming mixture hits it and explodes. Hear any ping?

Egr tube in a renix goes right directly under the tb.

Yep. Perhaps the leaky EGR valve was the issue though.

Under the TB should affect the ones in the center.

But - try disconnecting and plugging the tube. Swap plugs around, drive it, see if it makes #1 - formerly a brown one - look clean like it did before.

For sure something's hot and igniting/exploding it.

Did you try taking the valve cover off and looking to see if the exhaust valve is opening the same as the others. If it's not opening far enough it can cause some of the hot exhaust to linger and ignite it.

An odd problem for sure.

Try something - get it warm, shine a flashlight ACROSS the top of the TB - snap the accelerator HARD. Look to see if you get a mist of fuel and air flowing UP OUT of the TB.
CAREFUL that mix is explosive - a backfire can blind you - keep face away - safety goggles recommended.

That mist is called BLOWBACK. A symptom of the exhaust valve not opening right.

We've encountered that on very high performance engines - when you are "pushing
the limits" - valve train problem, flat cam, even a slow cam.

Well????????